In a typical cellular radio system, wireless terminals (also referred to as user equipment unit nodes, UEs, mobile terminals, and/or mobile stations) communicate via a radio access network (RAN) with one or more core networks, which provide access to data networks, such as the Internet, and/or the public-switched telecommunications network (PSTN). The RAN covers a geographical area that is divided into cell areas, with each cell area being served by a radio base station (also referred to as a base station, a RAN node, a “NodeB”, and/or evolved NodeB “eNodeB”). A cell area is a geographical area where radio coverage is provided by the base station equipment at a base station site. The base stations communicate through radio communication channels with wireless terminals within range of the base stations.
Cellular communications system operators have begun offering mobile broadband data services based on, for example, WCDMA (Wideband Code Division Multiple Access), HSPA (High Speed Packet Access), and Long Term Evolution (LTE) wireless technologies. In an LTE network, for example, a handover procedure is performed when a wireless device moves from one cell area to another cell area. During handover between cells, a wireless device Information Element (IE) may be forwarded to the target network node. The IE may contain history information that lists cells which the wireless device visited during previous handovers. Information associated with each listed cell may comprise a duration that the cell served the wireless device and a reason for the handover. The reason for the handover may be referred to as the handover (HO) Cause Value. A target network node may use contents of the IE to optimize, e.g., further treatment of the wireless device or handover thresholds to neighbor cells.
Network nodes may use different interfaces, such as X2 or S1, for handover signaling between network nodes. X2 and S1 define HO Cause Value IE as an enumerated value where each enumerated value encoded in the IE is associated to a particular handover cause (i.e. reason for the handover). However, X2 and S1 associate different enumerated HO Cause Values with different handover causes. Because a target node of the handover knows which signaling interface is used, the target node may correctly interpret the current enumerated cause value. However, the history information may also contain cause values associated with prior handovers. A target node may not know what interface previous network nodes used for previous handovers. Thus, the target node may not be able to use the information because it may not be able to correctly interpret the previous cause values.